Method of fabricating stator vanes



Oct. 2 5, 1960 H. A. s'roDDARD r-:rAL 2,957,228

METHOD OF' FABRICATING STATOR VANES Filed Dec. 27, 1957 United States Patent O jMETHOD OF FABRICATING STATOR VANES Herbert A. Stoddard, George T. Morton, and William A.

Howison, Cincinnati, Ohio, assignors to General Electric Company, a corporation of New York The present invention relates to a method of manufacturing stator vanes for variable stator axial ow compressors of the type used with turbo jet engines and more particularly to an improved method of fabricating such vanes from a number of separate pieces.

Up to the present time it hasbeen conventional practice to manufacture stator vanes from a single piece of material by rough forging the airfoil section .to rough dimensions, upsetting the metal at one end of the airfoil to form a knob, grinding the airfoil to nish dimensions, and then machining the root section of the vane from the knob. Since the stator vanes of a variable stator compressor are adjusted by an actuator from the exterior of the compressor casing the vanes must be accessible and must be capable of rotating. ln the usual case this is accomplished by extending the root section of the vane through the compressor casing. This requires a construction which is easily sealed against leakage of compressor air yet permits the vane to be rotated about its longitudinal axis. To accomplish these ends, the root section of the vane has been provided with a laterally projecting shelf or platform and a cylindrical spacer section which form bearing and sealing surfaces where they contact the casing. Since the upper and lower faces of the shelf have had to be machined smooth and since the cylindrical spacer section is bored or milled out to reduce weight, this vane construction has been di'icult and expensive vto manufacture by conventional forging methods.

An object of the present invention is the provision of an improved method of manufacturing stator vanes for variable stator compressors.

Another object of the present invention is the provision of a method of fabricating stator vanes from a plurality of separate pieces.

A further object is the provision of a method of fabricating stator vanes which employs inexpensive metal working techniques and which utilizes a minimum of machining operations.

The present invention overcomes the disadvantages inherent in the prior known methods of stator vane manufacture by provision of a method of fabricating stator vanes from a plurality of separate pieces. The present method includes the steps of: cold rolling an airfoil section from a piece of stock material; blanking out a tang from the stock at the base of the airfoil; rough stamping a shelf from sheet material; securing the shelf to the tang adjacent the airfoil; machining the outer diameter of the shelf; machining a locating step on one face of the shelf and machining the edges of the tang to the same radius; positioning a spacer on said tang and locating step; and securing an actuator arm to said tang adjacent to the spacer.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a perspective view of the airfoil and root section and the shelf after the blanking operation and prior to assembly;

Figs. 2, 3 and 4 are partial perspective views showing the root section and shelf of the vane in various stages of construction;

Fig. 5 is a partial perspective view showing the various elements of the actuator assembly and the root section of the vane in disassembled relation; and

Fig. 6 is a side View partly in section of a stator vane mounted in the casing of a variable stator compressor.

Referring more particularly to Fig. l of the drawing the airfoil section 11 of the vane is formed to the proper cross sectional shape and thickness by cold rolling one end of a Slug of stock material. The cold rolling process leaves a smooth surface on the airfoil which requires no further finishing operations. The rolling operation is stopped short of the opposite end of the stock material and a radius 12 is rolled on both sides of the airfoil at the juncture of the airfoil section with the unrolled stock material. The radius denes a fillet between the airfoil section and the root section which prevents the buildup of stress concentrations. The radius for any given vane construction will vary as a function of the gas bending load to which the vane is subjected and the amplitude and frequency of oscillation of the vane. By way of example, a suitable radius for one vane construction is approximately 0.17 inch. After the airfoil and radii 12 are rolled, the flash or excess material is trimmed from the edges of the airfoil section and a connecting post 13 and tang 14 are blanked from the unrolled stock material. These trimming and blanking operations can be performed simultaneously with a suitable trimming and blanking die. A shelf or platform 15 is stamped or otherwise blanked from a piece of sheet material and an elongated slot 16 formed in its interior. In this operation the shelf is formed slightly oversize to rough dimension and the slot centered along a diameter of the shelf. As shown in Fig. 2, the shelf is attached to the remainder of the vane by inserting the tang 14 through the slot 16 until the shelf lits snugly against the base of the airfoil section. The contacting surfaces of the shelf, airfoil section and tang are then secured together, as by brazing or welding, to hold the shelf rigidly in position.

In a series of machining operations performed sequentially, the shelf is turned to the proper outside diameter and the face of the shelf removed from the airfoil section is machined to form a circular locating step 17. The lateral edges of the tang are then machined to the same radius as the locating step, as shown in Fig. 3, and the connecting post is turned to the desired diameter. As shown in Fig. 4, in the final machining operation the connecting post is externally threaded and the end of the tang removed from the airfoil is undercut as at 18 to form a pair of locating ears 19 and 21.

After the airfoil, shelf and root section are completed the remaining elements of the vane are then fabricated and assembled. Referring to Fig. 5, a spacer 22 is formed from a piece of tubing by upsetting one end to form a ange 23 which provides a supporting surface for lthe actuator arm. The inside diameter of the spacer is slightly larger than the tang -14 and is positioned over the tang and the locating step 17 to bear against the shelf. An actuator arm 24 is stamped from a piece of sheet material, and to make connection with the root section, is provided With a central opening 25 to receive connecting post 13 and spaced openings 26 and 27 to receive attaching ears 19 and 21. To prevent reversal of the actuator arm during assembly, one ear and its corresponding opening may be made larger than the remaining ear and opening so that the arm will not fit on the tang in any but the proper position. When the spacer and arm are assembled a nut 28 is screwed onto post 13 to retain the parts in position.

A stator vane fabricated according to the method of the present invention is illustrated in Fig. 6 mounted in the casing of a variable stator compressor. In this assemblage the spacer22 andthe actuator arm 24 are'locked in position on the tang by the Vnut 28. The root section of the vane extends through the casing and the shelf and spacer bear against an annular bushing 29 of heat resistant material fitted in an opening in the casing. The bushing 29 seals the opening through the casing and provides a bearing surface for rotation of the vane.

While the airfoil section-illustrated in Fig. 1 is cold rolled from a slug or blank of stock material the present process is equally applicable to the use of pre-rolled strips of airfoil material. Such material is commercially available in various widths and thicknesses in strips of approximately 30 feetV long. These strips can be cut into sections of the desired length and for vanes having variable chord o-r variable thickness, the sections can be cold rolled in a knuckle roll to achieve the properyradius 12 and the desired chord and thickness. The tang and connecting post are then blanked out and the airfoil trimmed in the manner set forth above. In the case of Vanes which do not have a variable chord or variable thickness the sections need not be re-rolled since the strips themselves are of constant chord and constant thickness. In this case the tang and connecting post can be blanked out of the section and when the shelf is brazed onto the tang the radius 12 can be formed by brazing between the shelf and the airfoil and tang.

VWhile particular embodiments ofV the invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modications may be made without departing from the invention and it is intended to cover in the appended claims all such changes and modifications that come within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the U.S. is:

1. The method of manufacturing a stator vane for a variable stator compressor which includes the steps of: forming an airfoil section from stock material; blanking out a tang from the stock at an end of the airfoil; securing a laterally extending shelf section to the tank adjacent the airfoil; machining a circular step on the shelf and machining the lateral edges of the tang to the same diameter as the step; telescoping a tubular spacer over the tang and step; and attaching an actuator arm to the tang adjacent the spacer. n

2. The method of manufacturing a stator vane for a variable statorcompressor as set forth in claim 1 including the further step of forming a radius at the tang end of the airfoil section between said airfoil and said tang.

3. The method of manufacturing a stator vane for a variable stator compressor which includes the steps of: providing an airfoil section; blanking out a tang at one 4 end of the airfoil section; securing a laterally extending shelf section to the tang adjacent the airfoil; machining a circular step on the shelf and machining the lateral edges of the tang to the same diameter as the step; positioning a spacer over the tang and the step; and attaching an actuator arm to the tang adjacent the spacer.

4. The method of manufacturing a stator vane for a variable stator compressor as set forth in claim 3 includ-` ing the further step of forming a fillet defined by a radius at the juncture-of the airfoil and said tang.

5. The method of manufacturing a stator vane for a variable stator compressor which includes the vsteps of: providing a pre-rolled airfoil section; blanking out a tang and connecting post at one end of the airfoil section; brazing a laterally extending shelf section to said tang adjacent the airfoil; providing a fillet between the airfoil and the shelf; machining a circular step on the shelf and machining the lateral edges of the ktang to the same diameter as the step; positioninga tubular spacerover the tang and the step; and attaching an actuator arm to the connecting post to retain the spacer in position.

6. The method Vof manufacturing a stator vane for a variable stator compressor whichincludes the steps of: forming an airfoil section from one end of a piece of stock material; forming a vfillet at the juncture of the airfoil and the unrolled stock material; blanking out a tang and connecting post from the stock material at the unrolled end of the airfoil; securing a laterally projecting shelf section to the tang Vadjacent the airfoil; machining a circular step on the shelf and machining the lateral edges of the tang to the same diameter as the step; positioning a tubular spacer over the tang and the step; and attaching an actuator arm to the connecting post to retain the spacer in position. f

7. In a method for manufacturing a blade comprising an airfoil with lan integral tang at an end thereof, a platform between the airfoil and the tang, the platform including a dimension substantially that of the width of the airfoil, the steps of forming separately the platform and the airfoil and tang, removing a portion of the center of the platform to produce a slot the dimensions of which are essentially the same as -the cross sectional dimensions of the tang at a point adjacent the airfoil, securing the platform at that point so that the tang projects through the slot, and then nishing the platform and the tang to final size.

References Cited in the tile of this patent UNITED STATES PATENTS 2,651,492 Feilden u Sept. 8, 1953 2,766,645 Nichols et al Oct. 16, 1956 A2,827,224 Madison etal Mar. 18, 1958,

Y FOREIGN PATENTS 847,430 Germany Nov. 22, 1951 :754,335 Great Britain Aug. 8, 1956 

